It has been known in the art to utilize a device called a "Yo-Yo" for de-spinning an object in flight. Such a device has been incorporated into satellites and other such apparatus for the purpose of reducing or halting the spin thereof, thereby assuring proper orientation of antennas, etc. attached thereto. The yo-yo de-spin mechanism used in the prior art is essentially two pieces of wire with weights on the ends. These wires are symmetrically wrapped about the equator of a satellite and the weights are secured by release mechanisms. At a predetermined time after satellite spin-up and separation from a launching vehicle, the weights are released, thus discarding enough momentum to reduce the spin of the satellite to a desired minimal value. Such a device is fully described in NASA Technical Note D-708, August 1961.
The device of the NASA publication is designed to reduce the rotation of a satellite from approximately 3 rotations per second (rps) to as near 0 rps as possible. At the present time, no feasible procedure exists to de-spin bodies with initial spins as large as 300 rps. The force applied to the wires of the de-spinning device is proportional to the square of the angular velocity of the spinning body. Therefore, by increasing the angular velocity by a factor of 100, the forces on the wires are increased by a factor of 10,000. Thus, forces exceeding 20,000 lbs. would occur in these wires. Hence, the device shown in the NASA technical bulletin would fail at spins as large as 300 rps.
The devices of the prior art utilize cutting mechanisms to release the weights from the rotating body. The use of such devices results in an inherent lack of simultaneity in the release of the weights, the result of which is an erratic lateral motion being parted to the rotating body. This erratic behavior, a relatively unimportant factor at a rotational velocity of 3 rps, becomes a critical and highly undesirable factor at velocities on the order of 300 rps. Also, inherent minute physical variations resulting from manufacture of the de-spin devices (variations in wire gage, mass of the weight elements, etc.) will result in erratic motion of the rotating body. Such minor variations are relatively unimportant at low rotational speeds but become critical at very high rotational velocities. Therefore, the prior art devices and techniques for de-spinning a rotating object are not suitable for application to objects rotating at very high angular velocities.
It is therefore an object of this invention to provide means to de-spin an object which overcomes the drawbacks of the prior art devices.
It is an object of this invention to provide means to rapidly and dependably reduce the rotational speed of an object rotating at a very rapid rate.
It is another object of this invention to provide means capable of rapidly reducing the spin rate of an object without imparting any imbalance or other motions thereto.
Yet another object of this invention is to provide a device capable of de-spinning a rapidly rotating body, such device being suitable for mass production yet sufficiently accurate to perform its function reliably and accurately.